Silver halide color photographic materials comprise a support coated with at least three silver halide emulsion layers which are sensitive to three primary colors of blue, green and red light, respectively. Each of the emulsion layers may be composed of two or more layers. Further, various auxiliary layers are often provided in addition to the emulsion layers.
Such silver halide color photographic materials are widely used for various purposes including for usual photographing. In such cases wherein objects to be recorded as images of color photographs are limited to natural things, it is not very necessary to consider the color reproducible range and conventional techniques are sufficient for such purposes.
However, synthetic dyes or pigments which are obtained artificially have recently come into widespread use and as a result objects to be photographed having colors of high saturation are frequently encountered. Therefore, it has been desired to develop a silver halide color photographic material having a considerably wide color reproducible range of a color image in order to faithfully reproduce these colors of high saturation.
In fact, various attempts for improvement have been heretofore made to fulfill this requirement. For instance, a method intending to obtain a sharper spectral absorption with less secondary absorption than prior art by using a coupler which forms a dye having an improved spectral absorption, for example, a pivaloyl type 2-equivalent yellow coupler as described in U.S. Pat. No. 3,408,194, etc., an anilino type magenta coupler as described in U.S. Pat. Nos. 3,907,571 and 3,935,015, etc., a pyrazolotriazole type magenta coupler as described in U.S. Pat. No. 3,725,067, etc., a method in which color purity is improved upon development using an interlayer effect as described in Belgian Pat. No. 710,344, West German Pat. No. 2,043,943, etc., or a DIR coupler as described in U.S. Pat. No. 3,227,544, etc., a method for correcting an undesirable absorption of a dye formed using a colored coupler which has an automasking function as described in U.S. Pat. No. 2,455,170, etc., and a method of increasing color separation by means of sharpening the spectral sensitivity of each light-sensitive layer as described in Japenese Patent Application (OPI) No. 77443/82 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), etc., are known.
However, desirable color reproducibility is still not achieved with these methods.
Further methods using together two or more couplers which form dyes having spectral absorptions different from each other in the same emulsion layer have been proposed. For example, there are a method for emphasizing color mixing of images by means of mixing a small amount of a different kind of coupler with the main coupler as described in Japanese Patent Publication No. 391/65 and a method for partially improving incompleteness of absorption characteristics of a dye formed from the main coupler by using it together with two or more magenta couplers as described in Japanese Patent Application (OPI) No. 71333/75, etc.
However, these methods also have problems in that the range of density wherein color reproduction is obtainable is narrow, etc.
Moreover, for the purpose of obtaining color images having excellent color reproducibility extending from low density areas to high density areas, a proposal based on the theory of chromatics has been made that the maximum absorption wavelengths of dyes according to the subtractive three primary colors are desirably differentiated in the high density areas from the low density areas as described in The Color Gamut Obtainable by the Combination of Subtractive Color Dyes, Photo. Science and Engineering, Vol. 15, No. 5, pages 399-415 (1971).
A method as described in Japanese Patent Publication No. 43887/74 is an example which utilizes the above described theory. More specifically, in a silver halide color photographic material having three silver halide emulsion layers sensitive to three primary colors of blue, green and red, respectively, at least two kinds of couplers differing in coupling rate and forming dyes having the maximum absorption wavelengths different from each other by at least 5 nm are incorporated into the same emulsion layer in order to broaden the range of density wherein color reproduction is practicable.
However, this method is disadvantageous in that couplers which are usable are limited in view of problems in synthesis thereof or their properties other than color formation such as solubility and color stain, etc., and in that change in gradation and deviation in hue, etc., are apt to occur depending on the difference in processing techniques of development because of using together couplers having different coupling rates and, therefore, practical use is difficult. Particularly, a remarkably large decrease in color density due to poor stirring in a processing bath at development is a big problem in practice.